This is a request for a small grant to exploit an unexpected research opportunity. Two social groups of langurs (Presbytis entellus) were given to the Berkeley Behavior Station and observations to date suggest that the groups will provide excellent bases for long term studies on development and social behavior. The age/sex composition of the groups replicates that of a large proportion of free-ranging troops and offers opportunity to study the unique social roles and relationships characteristic of this highly variable species. Special emphasis will be placed on the sex differences in development and the important relationships between adults and immatures of the same sex.